build-unit-test-docker: Install pdbg in image
build-unit-test-docker: Install pdbg in image

Some OpenPOWER-related OpenBMC applications depend on pdbg for libpdbg.

Change-Id: I3682c45955de24c484c63960ed2115b1cedfface
Signed-off-by: Andrew Jeffery <02e0a999c50b1f88df7a8f5a04e1b76b35ea6a88@aj.id.au>

openbmc/openbmc-build-scripts,openbmc/openbmc-build-scripts